To the Editor: Although the efficacy of serine-threonine protein kinase (BRAF) inhibitors has been shown in patients with advanced melanoma who have the V600E BRAF mutation,(1),(2) data on the population with the V600K BRAF mutation are more limited and less encouraging. A phase 2 trial of vemurafenib showed a partial response in 4 of 10 patients with V600K BRAF mutations but provided no data on progression-free survival among these patients.(3) In the BREAK-2 (BRAF Inhibitor V600 E and K Metastatic Melanoma Phase 2) study of dabrafenib, the overall response rate and median progression-free survival were lower among 16 patients . . .